Design Parameters for Scratch Built Airframes

by House Of Noob | June 6, 2012 | (21) Posted in Tips

A guy named Karl got me started on building one year ago this coming July. I never even heard of most of the terms, but could fly a simulator. Not much help. One of the really big leg-ups that did help - and still helps today - is a series of guidelines for building I found. Basically, it is how to stay out of real trouble and give one a fighting chance.

 I made myself a cheat sheet as I reference it so much. 

They way that I used it was to start with Chord (in the drawing "c") and make everything else from that. I made sure I had a fuselage reference line early and measured everything from it as I went. I trial balanced a lot through the whole process to stay near the C.G. goals of getting fuselage and wing at the right point.

 Eventually it flew and with adjustments flew well and I put that down to this little guide.

 Hope it helps.


  Forth Trial flight of our KFx-1, made from yardsticks and insulation board.

The original collection of facts comes from Romney Bukolt and published in "Marcs Sparks" in about 1975 - but it can be hard to find. This reference below has a good drawing and explanation of one way to use the information. It's the one I used initially.



colorex on June 6, 2012
Thanks! This is a really good guide while designing bigger trainers, but nowadays you can make almost anything fly as long as it's light enough and you have enough power.
Not that it matches the beauty of a well built trainer :)
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House Of Noob on June 6, 2012
True. With enough thrust, pigs fly just fine.
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Number 2 on June 12, 2012
Thanks for finding and posting this info. I have been looking for something like this for a while. With this I should be able to get my own designs closer to correct sooner. With the correct CG and enough power you can make almost anything fly!
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House Of Noob on June 12, 2012
Dood - you fly bricks and dead chickens. I always figured you dispensed with physics looooon ago. LOL. Thanks all the same :)
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808aerosquadron on February 23, 2013
HoN - Thanks for posting this cheat sheet. This will be very helpful in future attempts to defy gravity through proper physics vs. pure brute force and watts.
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Design Parameters for Scratch Built Airframes